INVESTIGATION OF BORON STEEL (I)

Abstract

Effects of B on the transformation, hardenability, quenched and tempered hardness, and mechanical properties etc. of Cr and Cr-Mo case-hardening steels and high-tensile steels were investigated. The results obtained were. as follows.
The Ac₁ points were not ffected by addition of 0.001 to 0.011% B, but the Ac3 points were raised, while the Ar points were lowered. In this range of B contents, about 0.003% B is most effective to increase the hardenability.
The quenched and tempered hardness of both Cr and Cr-Mo case-hardening steels containing B was higher than that of those steels contains no B at tempering temperature of 200-300°C, but the hardness of the formers decreased remarkably when tempered at about 400°C at which there was no difference between them. High-tensile steels had the same inclination.
The yielding point and tensile strength increased, while the elongation and reduction and reduction of area decreased by adding B, but the impact value of case-hardening steels. decreased and that of high-tensile steels increased a little. The effect of B on carburizing property of case-hardening steels was not so remarkable and the carburized depth increased a little by adding B.